Glioblastoma multiforme (GBM) is one of the most malignant brain tumors affecting adults. It is characterized by necrotic tissue and abnormal vasculature, making it highly resistant to current cancer treatments. A promising alternative to standard cancer therapeutics is the use of drug delivery systems such as polymeric nanoparticles (NP) that deliver silencing RNA (siRNA) exclusively to tumor cells for gene knockdown. Presently, nonviral delivery vectors, such as poly(B-amino ester) (PBAE) NP, are beneficial delivery systems because they are less immunogenic and easier to chemically modify than vectors delivered by viruses. Although current formulations of PBAEs allow cargo release via hydrolytic degradation, the ideal delivery vector should have an environmentally triggered siRNA release system to increase safety and transfection efficacy. We hypothesized that the addition of disulfides to the main backbone of PBAE NPs would reduce cytotoxicity and increase siRNA transfection efficacy. Glutathione, a reducing agent present in the cytosol, can reduce a disulfide bond into two thiols and thus increase NP degradability for safety and immediate siRNA release. In this study, we characterized the binding, physical, and siRNA delivery properties of reducible PBAE NP. Polymer-siRNA binding strength was analyzed by a gel retardation assay. NP size and zeta potential were measured using NanoSight and zetasizer instruments, respectively. siRNA transfection efficiency was assessed by the amount of green fluorescent protein detected in GBM cells using a fluorescence plate reader. This study revealed that the addition of disulfide groups to PBAEs increased their siRNA binding strength, lowered cytotoxicity, and increased siRNA transfection efficiency. The best polymer showed 76% GFP knockdown while maintaining high cell viability twenty days following transfection. This novel class of polymers can serve as improved nonviral delivery vectors for a wide array of RNA interference (RNA1) targets, including those associated with malignant tumors.
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